Ring packing is a common technique used in processing plants, wastewater treatment facilities, refineries and offshore drilling operations to separate contaminants from gas and other liquids. Ring packing uses rings dumped inside a separation column that increases the surface area for liquid and vapor contact and enables fast and efficient chemical separation.
Selecting the best type of ring packing depends on your application and specific needs. Two of the most popular types of ring packing are pall rings and Raschig rings, which have unique features that make them better suited for different uses.
Pall Rings: An Overview
Pall rings are a type of tower packing with a cylindrical shape and a series of inward-facing tabs that increase the surface area within the column. Pall rings may also feature open windows and internal crossbars to improve material flow. The interior and exterior surfaces of pall rings increase the ring’s capacity while minimizing the space it uses inside the tower. This design effectively distributes liquids and gases to improve efficiency.
Types of Pall Rings
Pall rings are available in several materials, each with characteristics that make them best suited for various applications:
- Plastic pall rings: The most common type of ring packing is plastic pall rings. These pall rings are typically made from polypropylene. However, it can also be made from other synthetic polymers. Plastic pall rings provide corrosion resistance and efficient separation, though they may be unable to withstand extremely high temperatures.
- Metal pall rings: An alternative to plastic pall rings that provide enhanced endurance in harsh environments, metal pall rings are made from stainless steel. Metal pall rings made from stainless steel are more cost effective and provide more corrosion resistance than carbon steel.
- Ceramic pall rings: Ceramic is known for its brittleness, making ceramic pall rings less common than plastic and metal pall rings. However, ceramic pall rings provide excellent organic solvent resistance and chemical stability.
Pall Ring Applications
Pall rings range in size and configuration to provide optimal flow for various applications. This type of ring packing is suited for multiple uses across industries such as pharmaceutical manufacturing, food processing, waste and wastewater and petrochemical and chemical processing. A few common applications for pall rings include:
- Carbon dioxide and sulfuric acid absorption
- Ammonia and hydrochloric acid stripping
- Steam stripping
- Drying and absorbing columns
- Applications using corrosive acids
- Direct contact cooling
Raschig Rings: An Overview
Raschig rings are tubes of equal height and diameter with solid walls. This type of ring packing is the original ring packing design developed by Freiderich Raschig to replace trays within distillation towers. Raschig rings increase the surface area within the tower when compared to tray technology. The geometry of this design enables more efficient reactions between liquids and gases.
Types of Raschig Rings
Raschig rings are available in various sizes and materials:
- Ceramic Raschig rings: Ceramic Raschig rings offer excellent chemical stability and resistance to organic and inorganic acids, alkalis and salt. Ceramic Raschig rings are also cost-effective and provide good heat endurance.
- Metal Raschig rings: This type of ring packing is usually made from carbon steel or stainless steel. Raschig rings made from metal provide greater stability and strength than plastic Raschig rings.
- Glass Raschig rings: Although less common than ceramic and metal Raschig rings, glass Raschig rings are used in some applications.
- Plastic Raschig rings: This type of ring packing is also uncommon because plastic Raschig rings typically have less heat endurance than ceramic or metal ones. Manufacturers make plastic Raschig rings from polyvinyl chloride, polypropylene, polyethylene and other plastic polymers.
Raschig Ring Applications
Pall rings are an evolved type of Raschig ring, though Raschig rings still have their uses in various applications. Raschig rings are used across several industries, including food processing, metallurgy, petrochemical and gas and oxygen generation.
Here are a few of the most common applications for Raschig rings:
- Food and gas processing
- Ethanol production
- Processing nuclear materials
- Mass transfer
- Heat transfer
- Chemical absorption and stripping
Pall Rings vs. Raschig Rings
When your company needs to accomplish chemical separation, mass transfer or fractional distillation, deciding between pall rings and Raschig rings can be challenging. After all, pall rings and Raschig rings have a similar construction and may be used in several of the same applications. Both types of ring are available in different materials and sizes to provide businesses with solutions that suit their specifications.
Yet pall rings and Raschig rings have a few significant differences that can influence your company’s decision. Understanding these distinctions is essential for selecting the type of ring packing that provides optimal performance in your application. Consider some of the main differences between pall rings and Raschig rings:
Both pall rings and Raschig rings come in various materials, primarily metal, ceramic and plastic. Manufacturers also design these types of ring packing in a range of nominal sizes, void fractions and weights, so businesses can find the specific product that fits their needs.
The biggest difference between the two types of ring packing is that pall rings have windows or tabs punched in the walls, and Raschig rings have solid walls. This modification improves the older Raschig ring’s technology by enabling a greater surface area, increasing the pall ring’s capacity and efficiency. Whereas liquids and gases can only be in contact along the walls of a Raschig ring, a pall ring’s tabs create drop points that use more of the internal surface area.
The use of windows and tabs in pall rings means this type of ring packing has higher separation capabilities and lower resistance than Raschig rings. Pall rings also have better liquid and gas distribution.
Both pall rings and Raschig rings are suitable for various processing applications in multiple industries. For example, both types of ring packing are used in the petrochemical and food and drink processing industries. Companies use pall rings and Raschig rings in chemical absorption and stripping, mass transfer and applications using corrosive acids.
Despite these similarities, pall rings can be used in a broader range of applications. Raschig rings are best suited for applications that don’t require the greatest possible ring capacity or efficiency. In fact, Raschig rings are rarely used in tower packing today.
Because pall rings improve upon the Raschig ring’s design by providing increased surface area and efficiency, they’re well-suited for many applications. Pall rings are used across industrial processing applications, particularly those requiring a low-pressure drop under a vacuum and a high capacity.
Get the Pall Rings You Need With MACH Engineering
After comparing the features and uses of both types of ring packing, many companies conclude that pall rings are the better choice. This type of ring packing improves efficiency in absorption, separation, cooling and more. From the pharmaceutical industry to waste and wastewater treatment facilities, pall rings provide the capacity and efficiency many industries require.
When you need pall rings for your industrial processing application, choose from MACH Engineering’s extensive selection. MACH Engineering offers metal, plastic and ceramic pall rings designed and engineered for your specifications. We provide expert advice about what type of pall ring is best for your application, run process simulations and design and engineer products based on your specific needs.
To learn more about our pall rings and how we can help you find the most efficient product, contact MACH Engineering.